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1.
In situ measurements of organics, meteoritic material, mercury, and other elements in aerosols at 5 to 19 kilometers 总被引：1，自引：0，他引：1
In situ measurements of the chemical composition of individual aerosol particles at altitudes between 5 and 19 kilometers reveal that upper tropospheric aerosols often contained more organic material than sulfate. Although stratospheric aerosols primarily consisted of sulfuric acid and water, many also contained meteoritic material. Just above the tropopause, small amounts of mercury were found in over half of the aerosol particles that were analyzed. Overall, there was tremendous variety in aerosol composition. One measure of this diversity is that at least 45 elements were detected in aerosol particles. These results have wide implications for the complexity of aerosol sources and chemistry. They also offer possibilities for understanding the transport of atmospheric aerosols. 相似文献
2.
Waite JH Young DT Cravens TE Coates AJ Crary FJ Magee B Westlake J 《Science (New York, N.Y.)》2007,316(5826):870-875
Titan's lower atmosphere has long been known to harbor organic aerosols (tholins) presumed to have been formed from simple molecules, such as methane and nitrogen (CH4 and N2). Up to now, it has been assumed that tholins were formed at altitudes of several hundred kilometers by processes as yet unobserved. Using measurements from a combination of mass/charge and energy/charge spectrometers on the Cassini spacecraft, we have obtained evidence for tholin formation at high altitudes (approximately 1000 kilometers) in Titan's atmosphere. The observed chemical mix strongly implies a series of chemical reactions and physical processes that lead from simple molecules (CH4 and N2) to larger, more complex molecules (80 to 350 daltons) to negatively charged massive molecules (approximately 8000 daltons), which we identify as tholins. That the process involves massive negatively charged molecules and aerosols is completely unexpected. 相似文献
3.
Tropospheric aerosols affect the radiative forcing of Earth's climate, but their variable concentrations complicate an understanding of their global influence. Model-based estimates of aerosol distributions helped reveal spatial patterns indicative of the presence of tropospheric aerosols in the satellite-observed clear-sky solar radiation budget over the world's oceans. The results show that, although geographical signatures due to both natural and anthropogenic aerosols are manifest in the satellite observations, the naturally occurring sea-salt is the leading aerosol contributor to the global-mean clear-sky radiation balance over oceans. 相似文献
4.
Aerosol samples collected from the 17 April 1979 eruption plume of Soufriere, St. Vincent, at altitudes between 1.8 and 5.5 kilometers were physically and chemically very similar to the ash that fell on the island. Higher altitude samples (7.3 and 9.5 kilometers) had a much lower ash content but comparable concentrations of sulfate, which were above the background concentration found at these altitudes. 相似文献
5.
通过对不同烤烟品种、部位及海拔、土壤类型的烟叶样品进行致香物质化验,将检出的83种化合物按官能团归为6类,应用因子分析、灰色关联分析等方法,初步探究了品种、部位及海拔、土壤类型对6类致香物质的影响。结果表明：（1）检出的83种化合物中,有73种可以归属于对烟叶香气有较大影响的6类致香物质。其中,醛、酮34种,醇8种,酯、类酯7种,酚6种,呋喃8种,氮杂环10种。（2）6类致香物质在烟叶中的含量排序为：醛、酮＞醇＞酯、类酯＞酚＞呋喃＞氮杂环。（3）不同品种烟叶致香物质含量由高到低排序是：红花大金元（红大）＞云烟87＞云烟85＞K326;不同土壤类型烟叶排序是：红壤＞黄壤＞紫色土＞棕壤＞水稻土;部位间的排序为：上部＞中部;海拔1600m以下烟叶致香物质含量低于1600m以上区域;在海拔1600~2200m的区域内,致香物质含量随海拔的升高呈上升趋势。 相似文献
6.
Atmospheric burnup of the cosmos-954 reactor 总被引：2，自引：0，他引：2
Krey PW Leifer R Benson WK Dietz LA Hendrikson HC Coluzza JL 《Science (New York, N.Y.)》1979,205(4406):583-585
On 24 January 1978 the Russian satellite Cosmos-954 reentered the atmosphere over northern Canada. By use of high-altitude balloons, the atmosphere was sampled during 1978 up to an altitude of 39 kilometers to detect particulate debris from the reactor on board the satellite. Enriched uranium-bearing aerosols at concentrations and particle sizes compatible with partial burnup of the Cosmos-954 reactor were detected only in the high polar stratosphere. 相似文献
7.
8.
Soot carbon and excess fine potassium: long-range transport of combustion-derived aerosols 总被引：2，自引：0，他引：2
Andreae MO 《Science (New York, N.Y.)》1983,220(4602):1148-1151
During a cruise from Hamburg to Montevideo, aerosol samples representing air masses from Europe, the Sahara, tropical Africa, South America, and open oceanic regions were collected. They showed significant amounts of soot carbon over large areas of the remote Atlantic, often similar to concentrations in rural continental areas. Back-trajectories and the ratios of soot carbon to total fine (less than 1.7 micrometers in diameter) carbon and of excess fine potassium (the portion not attributable to soil dust or sea salt) to soot carbon indicate that biomass burning in tropical regions is an important source of soot carbon to the world atmosphere. The ratio of excess potassium to soot carbon in the fine fraction of aerosols is proposed as an indicator of the relative contributions of biomass and fossil-fuel burning to soot carbon aerosols. The ratio of soot carbon to fine carbon suggests that most of the particulate organic carbon over the Atlantic is of continental origin. 相似文献
9.
Evidence has been found that the earth is immersed in a large volume of glowing helium ions. This ionic glow, at 304 angstroms, is similar to the geocoronal hydrogen glow in that it extends to very high altitudes, but it is unique in that it is largely confined to the closed field line portion of the magnetosphere. Because of its magnetic containment, this ionic radiation is called the "magnetoglow." Observations of the magnetoglow from inside and outside the magnetospheric cavity promise to provide a valuable means of studying the structural dynamics of the magnetosphere. 相似文献
10.
稀土对沙田柚叶片某些生理特性的影响 总被引：1，自引：0，他引：1
稀土处理提高了沙田柚叶片的Ｆｖ／Ｆｍ、ΦＰＳⅡ和ＱＮ,从而增强了光合系统的光能转换效率;提高叶片的硝酸还原酶（ＮＲ）、亚硝酸还原酶（ＮｉＲ）和谷氨酸脱氢酶（ＧＤＨ）活性在最适稀土浓度处理下,ＮＲ和ＮｉＲ比对照提高了１４８％和６４％,达到极显著水平,表明稀土可以明显促进叶片氮代谢水平超氧化物岐化酶（ＳＯＤ）、过氧化氢酶（ＣＡＴ）和抗坏血酸过氧化物酶（ＡＰＸ）活性在最适稀土浓度处理下比对照提高了６５％、２４％和９４％,说明稀土增强了沙田柚叶片抗氧化能力高浓度稀土处理（１５００ｍｇ／ｋｇ）对沙田柚表现出抑制效果,建议稀土处理浓度为６００～８００ｍｇ／ｋｇ 相似文献
11.
Reduction of tropical cloudiness by soot 总被引：10，自引：0，他引：10
Ackerman AS Toon OB Stevens DE Heymsfield AJ Ramanathan V Welton EJ 《Science (New York, N.Y.)》2000,288(5468):1042-1047
Measurements and models show that enhanced aerosol concentrations can augment cloud albedo not only by increasing total droplet cross-sectional area, but also by reducing precipitation and thereby increasing cloud water content and cloud coverage. Aerosol pollution is expected to exert a net cooling influence on the global climate through these conventional mechanisms. Here, we demonstrate an opposite mechanism through which aerosols can reduce cloud cover and thus significantly offset aerosol-induced radiative cooling at the top of the atmosphere on a regional scale. In model simulations, the daytime clearing of trade cumulus is hastened and intensified by solar heating in dark haze (as found over much of the northern Indian Ocean during the northeast monsoon). 相似文献
12.
甘蔗分蘖中期以１００、３００、６００ｍｇ／Ｌ质量浓度叶面喷施氯化铈和硝酸稀土溶液,以喷清水作对照,分别于处理后第３ｄ和２０ｄ对甘蔗＋１叶片过氧化物酶和酯酶同工酶作电泳分析,结果表明,单质稀土元素铈和混合硝酸稀土对２种酶的同工酶均有影响,但存在一定差异,在不同浓度处理中,以３００ｍｇ／Ｌ处理结果最为明显,表现为多条酶带的染色加深,１００ｍｇ／Ｌ处理次之,６００ｍｇ／Ｌ处理相对影响较小,稀土元素处理后 相似文献
13.
Measurements of cloud condensation nuclei were made from small samples of stratospheric air taken from a U-2 aircraft at altitudes ranging from 13 to 19 kilometers. The measured concentrations of nuclei both in and outside the plume from the May and June 1980 eruptions of Mount St. Helens were higher than expected, ranging from about 100 to about 1000 per cubic centimeter active at 1 percent supersaturation. 相似文献
14.
Venkataraman C Habib G Eiguren-Fernandez A Miguel AH Friedlander SK 《Science (New York, N.Y.)》2005,307(5714):1454-1456
High concentrations of pollution particles, including "soot" or black carbon, exist over the Indian Ocean, but their sources and geographical origins are not well understood. We measured emissions from the combustion of biofuels, used widely in south Asia for cooking, and found that large amounts of carbonaceous aerosols are emitted per kilogram of fuel burnt. We calculate that biofuel combustion is the largest source of black carbon emissions in India, and we suggest that its control is central to climate change mitigation in the south Asian region. 相似文献
15.
Lead aerosols in the atmosphere: increasing concentrations 总被引：2，自引：0，他引：2
The concentrations of atmospheric lead around San Diego, California, have been determined and their geographic and seasonal variations are explained. The lead aerosol concentration at San Diego is increasing at a rate of 5 percent per year. The isotopic composition of lead aerosols is similar to that of the lead additives isolated from gasoline, which are the largest contributors to atmospheric lead pollution. 相似文献
16.
[目的]研究镧(La3+)、铈(Ce3+)、锌(Zn2+)对水稻根系的生理生化影响,探讨过量施用稀土的环境效应。[方法]以稀土元素镧(La3+)、铈(Ce3+)和兼具营养与毒性的重金属元素锌(Zn2+)为胁迫因子,采用组织培养法比较三者对水稻种子萌发及幼苗生长发育的影响。[结果]La3+、Ce3+和Zn2+对水稻种子萌发率影响很小,但对幼苗根、苗的生长具有显著的抑制作用,且在高浓度下稀土离子的抑制作用均大于Zn2+。水稻根可溶蛋白质含量随3种金属离子浓度的升高均呈先升后降的趋势,且La3+、Ce3+较Zn2+更为敏感;CAT和POD的活性随La3+、Ce3+和Zn2+浓度的增加逐渐上升,而SOD活性则先降后升;3种金属离子均能显著地刺激水稻根内MDA迅速积累。在高浓度下,La3+、Ce3+表现出比Zn2+更强的毒性。[结论]稀土元素La3+、Ce3+同重金属元素Zn2+对水稻的毒害机制相似。从长远来看,稀土有可能是一种新型的污染。 相似文献
17.
在无菌条件下培养祁术种子和根状茎的芽,出苗后移植在松针土、有机土和混合土(有机土 蛭石 珍珠岩按照5:1:1)中生长。结果表明,混合土中种子苗叶片数和叶面积最大．分别比有机土中增加34．8％和50．3％,比松针土中增加47．8％和58．5:混合土中种子苗根系长比有机土中提高42．2％,比松针土中提高11．1％,根系直径分别提高29．2％和54．2％:混合土中种子苗鲜重为松针土的2倍、有机土的2．9倍。同样的趋势也表现在芽殖苗生长中:混合土中的芽殖苗叶片数和叶面积比松针土中分别增加了26．9％和40．1％,根系长和根系直径分别提高38．1％和64．3％．鲜重则达到松针土的3．6倍。因此,在有机土中加入少量蛭石和珍珠岩而制成的混合土是祁术人工栽培较为理想的基质。 相似文献
18.
曲靖烟区不同前作对烤烟品质的影响 总被引：1，自引：0，他引：1
研究了云南曲靖两个海拔生态区不同前作下烤烟的化学成分、致香物质、评吸质量和重金属含量。结果表明,不同前作明显影响烟叶的品质,且因海拔不同而有差异。烤烟的化学成分在中低海拔烟区(1300～1800 m)以玉米或豌豆为前作的处理为佳,高海拔烟区(1800～2300 m)以蚕豆和玉米为前作的处理为佳;中低海拔烟区以玉米、绿肥或豌豆为前作,高海拔烟区以玉米或绿肥为前作可以适当增加烤烟的致香物质含量;烟叶评吸感官质量在中低海拔烟区以玉米、绿肥、豌豆或油菜为前作、高海拔烟区以绿肥或玉米为前作时得分较高,清香型风格在中低海拔区以绿肥或油菜为前作、高海拔烟区以洋芋或玉米为前作最明显;曲靖地区烤烟中铅含量偏高,在中低海拔烟区前作空闲、高海拔烟区以洋芋为前作的烤烟铅含量最低。综合而言,中低海拔烟区以玉米或豌豆为前作、高海拔烟区以绿肥或玉米为前作对改善烟叶品质最为有利。 相似文献
19.
Radiative climate forcing by the mount pinatubo eruption 总被引：2，自引：0，他引：2
Minnis P Harrison EF Stowe LL Gibson GG Denn FM Doelling DR Smith WL 《Science (New York, N.Y.)》1993,259(5100):1411-1415
Radiative flux anomalies derived from the National Aeronautics and Space Administration (NASA) spaceborne Earth Radiation Budget Experiment were used to determine the volcanic radiative forcing that followed the eruption of Mount Pinatubo in June 1991. They are the first unambiguous, direct measurements of large-scale volcanic forcing. The volcanic aerosols caused a strong cooling effect immediately; the amount of cooling increased through September 1991 as shortwave forcing increased relative to the longwave forcing. The primary effects of the aerosols were a direct increase in albedo over mostly clear areas and both direct and indirect increases in the albedo of cloudy areas. 相似文献
20.
[目的]从离子通道水平讨论作为稀土微肥的Eu3+对萝卜液泡生理活动的影响。[方法]用膜片钳全液泡记录方式研究讨论了膜内外Eu3+对萝卜(Raphanus satirus L.)慢液泡(SV)通道电流的影响。[结果]外液中存在EGTA和EuCl3时,通道电流被显著抑制;当外液中不含EGTA而同时含有CaCl2和不同浓度的EuCl3时,通道电流又被不同程度的增大,且随着Eu3+浓度的增加,通道电流逐渐降低;而Eu3+在膜内与SV通道作用机理的研究表明,Eu3+浓度高时抑制通道电流,浓度低时则促进通道电流。[结论]本文的研究结果为进一步研究Eu3+对植物生理活动的影响和Eu3+作为稀土微肥在农作物中的最佳用量在通道水平上提供了重要的依据。 相似文献